Objective—To validate use of magnetic resonance
images (MRIs) for measurement of equine articular
cartilage and subchondral bone thickness by
comparison with measurements in histologic
Sample Population—32 cadaveric carpal joints from
Procedure—Magnetic resonance imaging was performed
by use of 3-dimensional fast spoiled gradient
echo (SPGR) and T2* 3-dimensional fast gradient
echo (GRE) pulse sequences with and without fat
saturation. Standard sites on the medial and lateral
facets of the intermediate, radial, and third carpal
bones were used for subchondral bone and articular
cartilage thickness measurements. Digital image
analysis software was used for MRI measurements
10 mm from the dorsal extent and perpendicular to
the articular surface. Histomorphometric measurements
of hyaline, calcified cartilage, and subchondral
bone thickness were obtained at selected sites.
Comparisons between histomorphometric and MRI
measurements and between magnetic resonance
pulse sequences were evaluated.
Results—There were significant correlations
between GRE and SPGR and SPGR and histologic
measurements of articular cartilage, with no significant
difference between measurements and good
agreement. When calcified cartilage was excluded
from the histologic measurement, MRI measurements
were significantly greater than histologic measurements.
For subchondral bone thickness, there
was significant correlation between GRE and SPGR
but GRE was significantly greater than SPGR measurements.
Histomorphometric and MRI measurements
were strongly correlated and not significantly
Conclusions and Clinical Relevance—Magnetic resonance
imaging provides a good representation of
cartilage and subchondral bone thickness, supporting
its use in the study and clinical diagnosis of osteochondral
structure and alteration. (Am J Vet Res
Objective—To investigate effects of age on thickness and morphologic characteristics of hyaline cartilage, calcified cartilage, total cartilage, and subchondral bone (SCB) in the equine tarsometatarsal joint.
Sample Population—23 tarsal joints from cadavers of 23 ponies (11 days to 25 years old); ponies were limited to pasture exercise and euthanatized for reasons not related to this study.
Procedures—Tarsi were allocated into several age groups (11 days old [n = 3], 6 to 9 months old , 2 to 3 years old , 6 to 8 years old , 11 to 17 years old , and 20 to 25 years old ). Histologic examination and histomorphometric measurement of hyaline cartilage, calcified cartilage, total cartilage, and SCB were performed at medial and lateral sites.
Results—A significant decrease was detected in thickness of hyaline cartilage and total cartilage with increasing age, but there was a significant increase in thickness of calcified cartilage and SCB with increasing age. Differences in chondrocyte and collagen fiber arrangement, tidemark, and osteochondral junction morphology were evident among age groups.
Conclusions and Clinical Relevance—These findings suggested that the various tissues of the osteochondral unit change in different ways with age. The response of each tissue may be related to relative response of the tissues to strains induced by pasture exercise but could have an influence on how the overall properties of the osteochondral unit change with age. The findings may also be suggestive of changes that develop prior to the onset of osteoarthritis.